Elaine McKay, 58, who worked at the 1,700-pupil Clacton Coastal Academy in Essex, admitted sending a string of explicit photographs to the 15-year-old schoolboy, including provocative images of her sucking a cucumber and posing topless.

But she denied claims that the relationship escalated to the pair having sex, saying that the boy told a lie which got out of control.

Jurors found her not guilty of intentionally touching a boy aged 15 by having full sex with him and inciting a child to engage in sexual activity after just over an hour of deliberation at Chelmsford Crown Court.

Judge Patricia Lynch said she would sentence McKay for sending the pictures next month.

McKay, who was wearing a black suit and white blouse, sighed with relief as the verdict was returned.

She was supported in court by her third husband and other members of her family.

The prosecution claimed that she began to seduce the schoolboy while working at the school.

She accepted she spent around a year inundating the youngster with X-rated Facebook and WhatsApp messages and naked photographs of herself and pictures of her knickers.

But McKay broke down in tears in the witness stand as she vehemently denied having sex with the youngster - and insisted he initiated the inappropriate behaviour by “pestering” her for sexy pictures.

Asked why she sent the photographs, McKay sobbed: “I have no idea whatsoever. This is my regret. I don’t know, I don’t know the reason.”

She added: “I would never have had sex with him. Nothing ever physical. I would never have had sex with him, ever.”